Debra Milke was sentenced to death in 1990 in Arizona, after being convicted of soliciting two men to kill her four-year-old son, Christopher Milke, the previous year.
In 2013 she was released on bail after a court in San Francisco ruled that there was no direct proof linking her to the crime.
“I had absolutely nothing to do with the brutal murder of my son Christopher,” said Milke at the press conference in Phoenix, Arizona.
“I always believed this day would come, I just didn't think it would have to take 25 years 3 months and 14 days to rectify such a blatant miscarriage of justice.”
Continuously breaking down throughout the conference, Milke said “Losing a child to murder is a devastating tragedy with an indescribable pain that no parent should ever have to feel.”
“The only thing equally worse [sic] is to be falsely accused of participating in your own child's death.”
In 1989, two men drove Christopher Milke into the Arizona desert and shot him three times in the back of the head.
The only piece of evidence linking Milke to the murder was the statement of a police officer who claimed that she had confessed her complicity to him, although he could not provide any material evidence of the confession.
The officer was later convicted of fabricating evidence in other cases.
“The prosecution against me was one of a malicious nature. My innocence did not matter in their pursuit of a conviction,” Milke said.
“Seeking a conviction at any cost is unconscionable and is not what defines justice.”
Germans tangled in US justice system
Jens Söring, the son of a mid-level German diplomat has been in jail in the US state of Virginia since 1986 convicted of two counts of murder.
Söring initially confessed to the crime, in an apparent attempt to save his girlfriend, Elizabeth Haysom, from facing the death sentence. Both were convicted of killing Haysom's parents.
Söring later retracted his confession, saying he had believed he would be deported to Germany and face a lighter sentence there.
Although no evidence has ever been produced linking him to the crime he is still serving two life sentences.
Another case which stirred controversy in Germany involved two men who travelled to the USA in 2009.
The men believed they had bought the opportunity to have sex with minors. In fact it was a sting operation by the Cleveland police, who had set up a phony website in order to entrap paedophiles.
The men were each sentenced to 18 years in jail.
Such tactics are illegal in Germany, where police are not allowed to use child pornography in their work.